Species invasions threaten the antiquity of China's freshwater fish fauna

AimHuman-mediated species introductions and extirpations have resulted in the homogenization of biotas over time. However, there remains considerable uncertainty in our understanding of homogenization process for megadiverse regions of the world. Here, we investigate the consequences of widespread species invasions and extirpations for the biogeography of China&#39;s unique freshwater fish fauna. LocationChina. MethodsBy assembling a comprehensive dataset for distribution of Chinese freshwater fishes, we quantify how non-native fish species, from both overseas introductions and domestic translocations, has led to taxonomic homogenization of fish faunas at watershed, basin, ecoregion and country scales. We explore how the observed patterns in homogenization vary geographically, and identify those species most responsible for the faunal changes. Lastly, we simulate how China&#39;s fish fauna may continue to homogenize according to different scenarios of anticipated species introductions and extirpations. ResultsWe demonstrate that species introductions and extirpations have homogenized freshwater fish faunas across China. Overall compositional similarity of watersheds increased by 7.0% (from a historical 14.9% to 21.9% in the present day; SOrensen index). Compositional similarity of 96 of 103 (93.2%) watersheds increased, with western basins exhibiting the highest magnitude. Translocated non-native species associated with aquaculture practices contributed the most to faunal homogenization when compared to alien species (7.3% and 0.4%, respectively). Furthermore, faunal homogenization is predicted to intensify an additional 0.5-4.2% with increasing numbers of new non-native species introductions and the extirpation of native species. Main conclusionsSpecies introductions and extirpations have resulted in the significant impoverishment, and thus the loss of antiquity, of China&#39;s freshwater fish fauna over the past century. In the light of the growing realization that species composition (not richness) defines the role that biodiversity plays in maintaining ecosystem function, our study highlights the need for conservation strategies in China that consider changing patterns of diversity.</p

The center for creative conservation: fostering novel collaborations for regional sustainability

Broad environmental and social forces are affecting our regional ecosystems and impacting the communities who depend on them in diverse ways. Addressing these complex social-ecological challenges necessitates growth in the collective wisdom of society. The Center for Creative Conservation at the University of Washington is addressing this need by promoting innovative solutions to complex environmental problems through fostering collaborations across broadly diverse disciplines, sectors, and communities. We strive to learn and apply best practices of transdisciplinarity, meaning authentically engaging different modes of knowing toward novel and integrated ideas, methods, and applications. For example, we convene medical researchers with ecologists, urban planners, educators, and environmental justice advocates to understand how contact with nature benefits human health, and how we can design green cities, educational programs, and policies that simultaneously support conservation, health, and social equity goals. We support a group of Tribal researchers and community members, climate scientists, science communicators, anthropologists, and artists working to illustrate the consequences of climate change through filming a human-centered story about the effects of sea level rise on a Native village. We also support a group of archaeologists, ethnobotanists, Native elders, and tribal educators who are developing a program to reintroduce the Native land management practices of burning and digging needed to maintain camas prairie ecosystems. In these and other initiatives, we create and support opportunities for researchers, practitioners, and community members to share knowledge, generate cross-cutting solutions, build relationships, and collectively build social-ecological resilience. We are excited to share outcomes and lessons learned from two years of work, and look forward to engaging in new collaborations with our Salish Sea colleagues

Multi-Scale Threat Assessment of Riverine Ecosystems in the Colorado River Basin

Freshwater ecosystems are facing a deepening biodiversity crisis. Developing robust indicators to assess ecological integrity across large spatial scales and identifying the specific threats and pathways of impairment are thus critically needed if we are to inform freshwater conservation strategies. Here we present the first comprehensive threat assessment across the Colorado River Basin – one of the largest and most endangered river basins in North America – using a spatial framework accounting for the wide range of human activities (land uses, transportation infrastructure, exploitative activities, water withdrawals), pathways (local footprint, overland runoff, upstream cumulative effects), and spatial extent of influence (valley bottom, catchment and river network) known to affect the ecological integrity of riverine ecosystems. We quantified and mapped 69 individual threat indices with geospatial tools for each permanent, ephemeral, and intermittent stream segment within the Basin, encompassing a total of \u3e1,067,700 river kilometers. We further aggregated these indices into components of water quality (diffuse and point-source pollution), hydrology (flow regulation/uses and climate change), and physical system (connectivity and geomorphology). To demonstrate the potential of our framework to inform spatial planning decision processes, we examined the typical combinations of threats experienced by different hydrologic areas and stream segment types, identified candidate watersheds for habitat restoration and enhancement where hotspots of biodiversity and threat overlapped, and assessed the associations between threat indices and in situ measurements of ecological integrity describing a suite of biological (benthic macroinvertebrate, fish), chemical (total nitrogen load, water conductivity), hydrological (flow alteration) and physical indicators (streambed stability, instream habitat complexity). Our assessment highlights clear disparities in term of overall degree of threat that result from different combinations and contributions of individual stressors, with different priorities emerging for perennial versus intermittent or ephemeral stream segments, and between the upper and lower parts of the Basin. Importantly, we showed that our threat indices were generally correlated with biological, chemical, hydrological and physical indicators of ecological integrity they were intended to capture. In addition to its implications for the conservation and management of the highly imperiled Colorado River Basin, our case study illustrates how multi-faceted threat mapping can be used to assess the ecological integrity of riverine ecosystems in the absence of spatially extensive in situ measurements

Dam Construction Impacts Fish Biodiversity in a Subtropical River Network, China

Dams and diversions are a primary threat to freshwater fish biodiversity, including the loss of species and restructuring of communities, often resulting in taxonomic homogenization (increased similarity) over time. Mitigating these impacts requires a strong scientific understanding of both patterns and drivers of fish diversity. Here, we test whether different components of fish biodiversity have changed in response to major dam construction, and whether these patterns are predictable as a function of key environmental factors in the Gan River Basin, China. The results showed that total and native species alpha diversity have declined from the historical period (pre-dam) to the current period (post-dam). A total of 29 native species are lost, while 6 alien species were gained over time. We found evidence for fish faunal homogenization in the Gan River Basin, with a slight (1%) increase in taxonomic similarity among river basins from the historical period to the current period. Additionally, we revealed significant associations between drainage length, drainage area, and average air temperature, and alpha and beta fish diversity. This study provides new insight into the patterns and drivers of fish biodiversity change in the broader Yangtze River Basin and helps inform management efforts seeking to slow, and even reverse, current trajectories of biodiversity change

Fish Species Introductions Provide Novel Insights into the Patterns and Drivers of Phylogenetic Structure in Freshwaters

Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. We quantify phylogenetic clustering and overdispersion of native and non-native fishes of a large river basin in the American Southwest to test for the mechanisms (environmental filtering versus competitive exclusion) and spatial scales influencing community structure. Contrary to expectations, non-native species were phylogenetically clustered and related to natural environmental conditions, whereas native species were not phylogenetically structured, likely reflecting human-related changes to the basin. The species that are most invasive (in terms of ecological impacts) tended to be the most phylogenetically divergent from natives across watersheds, but not within watersheds, supporting the hypothesis that Darwin\u27s naturalization conundrum is driven by the spatial scale. Phylogenetic distinctiveness may facilitate non-native establishment at regional scales, but environmental filtering restricts local membership to closely related species with physiological tolerances for current environments. By contrast, native species may have been phylogenetically clustered in historical times, but species loss from contemporary populations by anthropogenic activities has likely shaped the phylogenetic signal. Our study implies that fundamental mechanisms of community assembly have changed, with fundamental consequences for the biogeography of both native and non-native species

Knowledge Exchange and Social Capital for Freshwater Ecosystem Assessments

The 1972 Clean Water Act (CWA) provided crucial environmental protections, spurring research and corresponding development of a network of expertise that represents critical human capital in freshwater conservation. We used social network analysis to evaluate collaboration across organizational types and ecosystem focus by examining connections between authors of freshwater assessments published since the CWA. We found that the freshwater assessment network is highly fragmented, with no trend toward centralization. Persistent cohesion around organizational subgroups and minimal bridging ties suggest the network is better positioned for diversification and innovation than for learning and building a strong history of linked expertise. Despite an abundance of research activity from university-affiliated authors, federal agency authors provide a majority of the bonding and bridging capital, and diverse agencies constitute the core network. Together, our results suggest that government agencies currently play a central role in sustaining the network of expertise in freshwater assessment, protection, and conservatio

Predation risk by largemouth bass modulates feeding functional responses of native and non-native crayfish

Context-dependency is prevalent in nature, challenging our understanding and prediction of the potential ecological impacts of non-native species (NNS). The presence of a top predator, for example, can modify the foraging behaviour of an intermediate consumer, by means of non-consumptive effects. This raises the question of whether the fear of predation might modulate consumption rates of NNS, thus shaping the magnitude of ecological impacts. Here, we quantified the functional feeding responses of three non-native crayfish species – red swamp crayfish Procambarus clarkii, rusty crayfish Faxonius rusticus and virile crayfish Faxonius virilis – compared to the native analogue signal crayfish Pacifastacus leniusculus, considering the predation risk imposed by a top fish predator, the globally invasive largemouth bass Micropterus salmoides. We applied the comparative functional response (FR) approach using snails as prey and exposing crayfish to water containing predator and dietary chemical cues or not. All crayfish species presented a destabilising Type II FR, regardless of the presence of chemical cues. Predation risk resulted in significantly longer handling times or lower attack rates in non-native crayfish; however, no significant differences were observed in signal crayfish. We estimated per capita impacts for each species using the functional response ratio (FRR; attack rate divided by handling time). The FRR metric was lower for all crayfish species when exposed to predation risk. Rusty crayfish demonstrated the highest FRR in the absence of chemical cues, followed by signal crayfish, virile crayfish and red swamp crayfish. By contrast, the FRR of signal crayfish was nearly twice that of rusty crayfish and virile crayfish and ten times greater than red swamp crayfish when chemical cues were present. The latter result agrees with the well-recognised ecological impacts of signal crayfish throughout its globally-introduced range. This study demonstrates the importance of considering the non-consumptive effects of predators when quantifying the ecological impacts of intermediate non-native consumers on prey. The direction and magnitude of the modulating effects of predators have clear implications for our understanding of NNS impacts and the prioritisation of management actions

Looking to the past to ensure the future of the world's oldest living vertebrate: Isotopic evidence for multi-decadal shifts in trophic ecology of the Australian lungfish

Meeting the conservation challenges of long‐lived animal species necessitate long‐ term assessments of trophic ecology. The use of dietary proxies, such as ratios of naturally occurring stable isotopes in animal tissues demonstrating progressive growth, has shown considerable promise to reconstruct trophic histories of long‐ lived organisms experiencing environmental change. Here, we combine innovative radiocarbon scale‐ageing techniques with stable isotope analysis of carbon and nitrogen from cross sections of scale to reconstruct the trophic ecology of Australian lungfish (Neoceratodus forsteri) across its remaining global distribution. Over a 65‐year period, we found pronounced temporal shifts in the δ13C and δ15N isotopic ratios of lungfish that coincided with a period of hydrological modification by dams and land‐use intensification associated with agriculture and livestock grazing. In the Brisbane and Burnett Rivers, whose hydrology is substantially regulated by large dams, lungfish showed consistent trends of δ13C depletion and δ15N enrichment over time. This may indicate anthropogenic changes in background isotopic levels of basal energy sources and/or that additional seston exported downstream from impoundments represent a carbon source that was previously unavailable, thus shifting lungfish diet from benthic‐dominated primary production typical of unmodified river systems, to pelagic carbon sources. By contrast, δ13C ratios of lungfish in the unregulated Mary River were more stable through time, whereas δ15N ratios increased during a period of dairy industry expansion and increased application of nitrogen fertilization and then subsequently decreased at the same time that rates of pasture development declined and nutrient inputs presumably decreased. In conclusion, we provide evidence for human‐caused alterations in background isotopic levels and potential changes in availability of benthic versus pelagic energy resources supporting Australian lungfish and demonstrate how detectable trophic signals in long‐lived fish scales can reveal long‐term anthropogenic changes in riverine ecosystems.American Philosophical Society; Australian Research Council, Grant/Award Number: LP130100118; Mohamed bin Zayed Species Conservation Fund; National Geographic Society

Filtration rates of the non-native Chinese mystery snail (Bellamya chinensis) and potential impacts on microbial communities

Invasive species in the phylum Mollusca, including gastropods and bivalves, have caused substantial impacts in freshwater ecosystems. The Chinese mystery snail, Bellamya chinensis, is a large viviparid snail native to Southeastern Asia and widely introduced throughout United States and parts of Canada and Europe. B. chinensis is a facultative filter-feeding detritivore that can both graze epiphytic diatoms using its radula and filter-feed its breathing water. Despite mounting concern associated with the expanding range and increasing abundance of B. chinensis in many parts of its invaded range, the potential ecological impacts of this non-native species remain largely unknown. Here, we used a series of laboratory experiments to assess filtration rates of B. chinensis and quantify its effects on microbial communities. According to both microcosm (24-hour, 4-L suspension) and mesocosm (5-day, 90-L suspension) experimental trials, B. chinensis exhibited an average filtration rate of 106-113 mL snail-1h-1(1.45 mL mg DW-1h-1) and an individual maximum of 471 mL snail-1h-1(6.15 mL mg DW-1h-1). These values are comparable to reported filtration rates for high-profile invasive, freshwater bivalves. Relationships between snail size and filtration rate relationship suggests that B. chinensis display an ontogenetic shift in feeding behavior from primarily radular grazing to increased filter-feeding at threshold size of approximately 44 mm shell height. Our experiments also revealed that high snail densities can result in small, significant shifts in bacterial community composition. These results suggest that B. chinensis may influence microbial communities either directly by using bacteria as a food source or indirectly by producing sufficiently large quantities of fecal and pseudo-fecal material to affect bacterial activity and growth. The overall ecological effects and importance of B. chinensis filtration behavior remain unclear, but our experimental results suggest that these impacts may be large and should be further investigated to better understand its potential role in coupling benthic and pelagic food webs in lake ecosystems.Las especies invasoras del phyllum Mollusca, incluyendo los gasterópodos y bivalvos, han causado impactos importantes en los ecosistemas dulceacuícolas. Bellamya chinensis, es un vivíparo de gran tamaño, nativo del sureste de Asia y ampliamente introducido a lo largo de los Estados Unidos y parte de Canadá y Europa. B. chinensis es una especie detritivora- filtradora facultativa, que puede tanto ramonear diatomeas epifitas usando su rádula como filtrar el agua que respiran. A pesar de la creciente preocupación asociada al incremento en la abundancia y rango de distribución de B. chinensis en las regiones ya colonizadas, el potencial impacto ecológico de esta especie introducida permanece ampliamente desconocido. En este estudio, usamos series de experimentos de laboratorio para evaluar las tasas de filtración de B. chinensis y cuantificar su efecto en las comunidades microbianas. De acuerdo con los experimentos realizados tanto en los microcosmos (24-hour, 4-L suspensión) como en los mesocosmos (5-day, 90-L suspensión), B. chinensis mostró una tasa promedio de filtración de 106-113 mL caracol-1h-1(1.45 mL mg peso seco-1h-1) y un máximo por individuo de 471 mL caracol-1h-1(6.15 mL mg peso seco-1h-1). Estos valores son comparables a otros reportados para especies de bivalvos dulceacuícolas altamente invasivas. La relación entre el tamaño de los caracoles y las tasas de filtración sugieren que B. chinensis muestra un cambio ontogénico en la manera de alimentarse, de ramoneo a una mayor alimentación por filtración, a partir de un umbral de tamaño de la concha de aproximadamente 44 mm de altura. Nuestros experimentos también revelan que altas densidades de caracoles generan pequeños cambios pero significativos en las comunidades microbianas. Estos resultados sugieren que B. chinensis afectaría las comunidades microbianas de forma directa usando las bacterias como fuente de alimentación o indirectamente al producir una cantidad de materia fecal o seudo-fecal, suficiente para afectar la actividad y crecimiento bacteriano. El impacto ecológico global y el comportamiento como filtrador de B. chinensis aún no son claros, pero nuestros resultados experimentales sugieren que estos impactos pueden ser importantes y se deben investigar mejor para entender más su papel potencial en el acoplamiento de las redes tróficas bentónicas y pelágicas en los sistemas lacustres